The Matrix Assisted Laser Desorption Ionization (MALDI) technique involves depositing a sample (analyte) and a matrix dissolved in a solvent as a spot on a sample plate. After the solvent has evaporated, the mixture of sample and matrix is left on the sample plate. Typically, the sample plate bearing the sample spot is inserted into an mass analyzer or into a sample source adjacent a mass analyzer. The mass analyzer is typically pumped out to provide a substantially vacuum environment before the sample at each spot is analyzed. The MALDI technique requires that a pulse from a laser irradiate the matrix and causes it to evaporate. The sample is then carried with the matrix, ionized, and eventually analyzed by the mass analyzer.
Matrix Assisted Laser Desorption/Ionization (MALDI) is often combined with time-of-flight (TOF) mass spectrometry, Fourier Transform Ion Cyclotron Resonance, quadrupole ion trap, and triple quadrupole mass spectrometers, providing for detection of large molecular masses.
MALDI sample plates are typically formed of stainless steel having a highly polished and flat surface. The plates may be adapted to fit into and to be handled by automated handling apparatus employed to transport and position the plates within the mass spectrometer instrument, and optionally to transport the plates between different stations in an automated analysis train (e.g., between automated sample deposition equipment and the mass spectrometer).
The transferring a sample plate from one gripping mechanism to another produces a localized stress point which typically results in yielding the surface material due to a constant clamping force applied during the transference. This frictional point contact made with a sample plate can cause galling of the sample plate and the member that makes contact with it. Therefore when gripping or releasing a sample plate, material removal or addition can occur. The effects of material removal or buildup due to frictional surface conditions cause locking and resistance build up between the sample plate and the member it is contacting which effects planarity alignments and accuracy of parts. Ultimately, this means that when a sample plate is transferred from one gripping means to another, the degree of repeatability and reliability can be destroyed. Typically dissimilar metals, polymers or coating surfaces are used with varying degrees of lubricity avoiding premature surface deterioration failures.